FI problems.

[rfoulds]

Well, I thought I had this licked, but apparently not. My 1974 914 with the 1.8 is giving me a weird problem.

Once it is warmed up, it will run fine for about 15 minutes, then when you try to hold speed, the engine will just completely die. In about five seconds, it comes back. After this happens, it won't hold idle any longer either. Before, it idles perfectly. It repeats this until I shut it down for an hour.

So far, I have moved the fuel pump up front.
Replaced fuel filter.
Replaced all ignition components except distributer.
Replaced injectors.
Found and fixed all loose connections in FI harness.
Cleaned and checked throttle body.

The throttle body was full of oil and grime. and the butterfly seems to be actually dragging on the body so, I guess I will be replacing that too.

What I fear is this is an ECU problem..

Anyone have any ideas??

[scotty914]

i have an ecu you could borrow if you want to test it

but i would check the connections for the fuel pump ( do you hear it running when it dies ... you could try jumping out the relay or on the reg board is the t4 connector you could ground out the top left pin IIRC, it will by pass the relay pack by the battery ( at least the fuel pump relay there ) you could even rig a led off of the fuel pump connections so you could see it and if you are lossing the power to the pump the light will go out

now there is the chance that the feul pump is bad and after it heats up from running it could lose pressure

now my relay pack works loose every so often and the car dies but i know it so i just push it in and it is okay

but there are many things to check check those and if that does not do it email me and i will send you a check list

[bowlsby]

The ECUs are pretty hardy, it would be the last thing I'd suspect.

Im not an Ljet person, but I have a 75 VW bug that is L-jet so I have a little exposure to them so my guess is...

Pull one plug wire and test for spark, especially after it dies.

Could be heat related? It seems to work ok until it gets up to temperature, or

It may be a fuel starvation item...which could be a defect in the air flow meter. Have you checked that out?

Maybe the resistor pack is failing under heat and opening up causing the injectors to stop. Take measurements of them cold and then immediately when it dies to check their value.

If you have an exhaust gas analyser (a shop will) you could monitor the mixture to see if its lean or rich, which might give a better clue as to where to look.

[Otto]

Take the cover off the air flow box and take a pencil eraser and clean the circurty tracks. They are kind of like copper circuit boards stuff and every once in a while they accumulate debris that will cause an intermittent glitch. OTTO